text: // Copyright (c) 2008  GeometryFactory Sarl (France).
  // All rights reserved.
  //
  // This file is part of CGAL (www.cgal.org).
  // You can redistribute it and/or modify it under the terms of the GNU
  // General Public License as published by the Free Software Foundation,
  // either version 3 of the License, or (at your option) any later version.
  //
  // Licensees holding a valid commercial license may use this file in
  // accordance with the commercial license agreement provided with the software.
  //
  // This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
  // WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  //
  // $URL: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/releases/CGAL-4.1-branch/GraphicsView/include/CGAL/Qt/GraphicsViewCircleInput.h $
  // $Id: GraphicsViewCircleInput.h 67117 2012-01-13 18:14:48Z lrineau $
  // 
  //
  // Author(s)     : Andreas Fabri <Andreas.Fabri@geometryfactory.com>
  //                 Laurent Rineau <Laurent.Rineau@geometryfactory.com>
  
  #ifndef CGAL_QT_GRAPHICS_VIEW_CIRCLE_INPUT_H
  #define CGAL_QT_GRAPHICS_VIEW_CIRCLE_INPUT_H
  
  #include <QGraphicsView>
  #include <QRectF>
  #include <QPointF>
  #include <QGraphicsItem>
  #include <QGraphicsEllipseItem> 
  #include <QGraphicsScene>
  #include <QGraphicsSceneMouseEvent>
  #include <QPainter>
  #include <QStyleOption>
  
  #include <CGAL/Qt/Converter.h>
  #include <CGAL/Qt/GraphicsViewInput.h>
  
  #include <CGAL/array.h>
  
  namespace CGAL {
  namespace Qt {
  
  template <typename K>
  class GraphicsViewCircleInput : public GraphicsViewInput
  {
  public:
    GraphicsViewCircleInput(QObject *parent, QGraphicsScene* s, int pointsOnCircle=1); 
  
  protected:
      
    virtual void mousePressEvent(QGraphicsSceneMouseEvent *event);
    virtual void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
    virtual void keyPressEvent(QKeyEvent *event);
    
    bool eventFilter(QObject *obj, QEvent *event);
    
  
    
  
  private:
  
    typedef typename K::Point_2 Point_2;
    int m_pointsOnCircle; // 1, 2 or 3
    int count;
    QGraphicsEllipseItem *qcircle;
    QPointF qp, qq, qr;
    Point_2 p, q, r;
    QGraphicsScene *scene_;  
    Converter<K> convert;
  };
  
  
  template <typename K>
  GraphicsViewCircleInput<K>::GraphicsViewCircleInput(QObject *parent, QGraphicsScene* s, int pointsOnCircle)
    : GraphicsViewInput(parent), m_pointsOnCircle(pointsOnCircle), 
      count(0), qcircle(new QGraphicsEllipseItem()), scene_(s)
  {
    qcircle->hide();
    s->addItem(qcircle);
  }
  
  
  template <typename K>
  void 
  GraphicsViewCircleInput<K>::mousePressEvent(QGraphicsSceneMouseEvent *event)
  { 
    if(event->modifiers()  & ::Qt::ShiftModifier){
      return;
    }
    if(m_pointsOnCircle < 3){
      if(count == 0){
        qp = event->scenePos();
        p = convert(qp);
        count = 1;
      } else {
        qq = event->scenePos();
        if(qp != qq){
  	qcircle->hide();
  	q = convert(qq);
  	if(m_pointsOnCircle == 1){
  	  typename K::FT sd = squared_distance(p,q);
  	  emit generate(CGAL::make_object(std::make_pair(p, sd)));
  	} else {
  	  emit generate(CGAL::make_object(std::make_pair(p, q)));
  	}
  	count = 0;
        } 
      }
    } else {
      if(count == 0){
        qp = event->scenePos();
        p = convert(qp);
        count = 1;
      } else if(count == 1){
        qq = event->scenePos();
        if(qp != qq){
  	q = convert(qq);
  	count = 2;
        }
      } else { // count == 2
        qr  = event->scenePos();
        r = convert(qr);
        typename K::Collinear_2 collinear;
        if(! collinear(p,q,r)){
  	emit generate(CGAL::make_object(CGAL::make_array(p,q,r)));
  	count = 0;
        }
      }
    }
  }
  
  
  template <typename K>
  void 
  GraphicsViewCircleInput<K>::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
  {
    CGAL::Bbox_2 bb;
    typename K::Construct_circle_2 construct_circle;
    if(count == 0){
      qcircle->hide();
      return;
    } else if(count == 1) {
      qq = event->scenePos();
      q = convert(qq);
      if(qp == qq){
        qcircle->hide();
        return;
      } else {
        if(m_pointsOnCircle == 1){
  	typename K::FT sd = squared_distance(p,q);
  	bb = construct_circle(p, sd).bbox();
        } else {
  	bb = construct_circle(p, q).bbox();
        }
      }
    } else { // count == 2
      qr = event->scenePos();
      r = convert(qr);
      typename K::Collinear_2 collinear;
      if(collinear(p,q,r)){
        qcircle->hide();
        return;
      } else {
        bb = construct_circle(p, q, r).bbox();
      }
    }
    qcircle->setRect(bb.xmin(), bb.ymin(), bb.xmax()-bb.xmin(), bb.ymax()-bb.ymin());
    qcircle->show();
  }
  
  
  template <typename K>
  void 
  GraphicsViewCircleInput<K>::keyPressEvent ( QKeyEvent * event ) 
  {
    if(event->key() == ::Qt::Key_Delete){
      if(count>0){
        --count;
      }
    }
  }
  
  
  
  template <typename K>
  bool 
  GraphicsViewCircleInput<K>::eventFilter(QObject *obj, QEvent *event)
  {
    if (event->type() == QEvent::GraphicsSceneMousePress) {
      QGraphicsSceneMouseEvent *mouseEvent = static_cast<QGraphicsSceneMouseEvent *>(event);
      mousePressEvent(mouseEvent);
      return true;
    } else if (event->type() == QEvent::GraphicsSceneMouseMove) {
      QGraphicsSceneMouseEvent *mouseEvent = static_cast<QGraphicsSceneMouseEvent *>(event);
      mouseMoveEvent(mouseEvent);
      return true;
    } else if (event->type() == QEvent::KeyPress) {
      QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
      keyPressEvent(keyEvent);
      return true;
    } else{
      // standard event processing
      return QObject::eventFilter(obj, event);
    }
  } 
  
  } // namespace Qt
  
  } // namespace CGAL
  
  #endif // CGAL_QT_GRAPHICS_VIEW_CIRCLE_INPUT_H
  